Digital-to-analog conversion provides an analog output responsive to a digital input. Along those lines, a reference bias current may be provided for such conversion. Furthermore, such analog output is a current-based output, which may be for a source mode of operation or a sink mode of operation. To support both sink and source modes of operation, generally two DACs are used, namely a PMOS DAC for the source mode, and an NMOS DAC for the sink mode, where each of such DACs includes a dedicated current bias circuit with a current mirror.
As there is more demand for digital-to-analog conversion, such conversion has increasingly led to narrower and narrower tolerable inaccuracy in gain error. Along those lines, a dedicated current bias circuit included in a DAC has significant limitations. Unfortunately, providing an accurate current mirror for such dedicated current bias circuit that covers a wide range of currents and does not vary too much, for instance, over temperature may add considerable circuit overhead, and still may not support a sufficiently narrow range of tolerable inaccuracy.
Accordingly, it would be useful to provide a DAC that overcomes one or more of the above-described limitations.